Other cities involved in the protests include London, Paris, Brasilia, New York, and Cape Town.

Six female Nobel peace laureates have jointly appealed to the UN, urging it to help Ms Suu Kyi regain her freedom.

"The detention of Aung San Suu Kyi is the most visible manifestation of the regime's brutality but it is only the tip of the iceberg," they wrote in an open letter published in UK newspaper The Guardian.

Ms Suu Kyi's National League for Democracy won a convincing victory in a general election in 1990 but the junta refused to hand over power.

Close ally

The protests coincide with the anniversary of the UN charter, and campaigners say they will be stepping up the pressure for UN action.

They blame China for blocking a UN resolution against Burma's generals.

Mr Gambari, who is expected to return to Burma next month, is meeting senior Chinese officials this week.

But he will not see any of the country's top leaders, the BBC's Daniel Griffiths reports from Beijing.

Although China, one of Burma's closest allies, has expressed concern about the situation there, it has always stressed that it will not interfere in its neighbour's internal affairs.

It is a sign that Beijing is unwilling to push Burma too hard, our correspondent says.

Burmese officials say 10 people died during the crackdown on protests in September, but diplomats believe the true figures are much higher. Hundreds of people are thought to be in detention.